Method for determining presence of water

ABSTRACT

A sensor can detect the difference in potential between itself and the fluid into which it is immersed, a signal generated by the probe representing this difference in potential. This signal is used to activate an oscillator circuit. By varying the conditions at which current in the oscillator circuit begins to oscillate, various liquids can be detected and identified.

This application is a division of application Ser. No. 08/226,958, filedApr. 13, 1994, now U.S. Pat. No. 5,564,904.

BACKGROUND OF THE INVENTION

The prior art lacks an extremely reliable type of sensor or detectiondevice that can distinguish between oil and water. Furthermore, it isimportant that such a device is able to detect the difference betweenthe type of fluid, for example, such as the various grades of refinedfuel/oil and water. Such a device, when incorporated into a pump controlsystem, should be able to carry out each of the following functions:

1. Cause a pump to be turned on or off when water or oil/fuel isdetected in a storage system;

2. Give an indication that oil or water has been sensed;

3. Provide a means to detect the presence and amount of emulsion inunctuous fluids.

4. Sense a particular grade of oil and cause activation of an alarm,pump, or indicator light.

To date, no such device has been available.

SUMMARY OF THE INVENTION

The invention is generally described as a detection device which maycomprise one or more sensors which are preferably in operablecommunication with AC or DC pumps, alarm circuits, or control apparatus.

The sensor can detect the difference in potential between itself and thefluid into which it is partially immersed, and it can generate an outputsignal representing this difference in potential. This signal is used toactivate an oscillator circuit. By varying the conditions, orparameters, at which current flowing through the oscillator circuitbegins to oscillate, various liquids can be identified. By the use ofmultiple sensors, each set to determine a different material, aneffective method results for detecting the presence of an excess of onefluid in another fluid, or in appropriately selected areas of a vesselor tank. The sensor is in communication with electronic circuitry, suchas a conventional microprocessor, capable of automatically activating apump or alarm when certain fluids are detected or reach a dangerouslyabnormal level.

OBJECTS OF THE INVENTION

It is an object of the invention to have a sensor which can distinguishbetween various types of fluids.

It is a further object of the invention to have a detecting device whichcan automatically activate pump control circuits.

It is a further object of the invention to provide an electric sumppumping assembly with an alarm and maintenance feature which can beeasily monitored.

It is a further object of the invention to provide a highly reliablebilge alarm system that can be used on any type of vessel to alert acrew of a flood level condition or fuel spill.

These and other objects are achieved by a probe capable of detecting anelectrical potential between itself and the fluid, the probe having anoutput circuit therein producing an output signal when the electricalpotential reaches a predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a detection device constructed inaccordance with a preferred embodiment of the present invention.

FIG. 2 is a partial cutaway view of the probe of the detecting deviceshown in FIG. 1.

FIG. 3 is a view of the probe of FIG. 1 submerged in a liquid to beanalyzed.

FIG. 4 is a schematic diagram of the circuit used in the detectingdevice shown in FIG. 1.

FIG. 5 is a schematic diagram of a portion of a circuit used in amodified embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that an electrical potential between a fluid and aprobe immersed therein may cause oscillation of current in an oscillatorcircuit, such oscillation being translated into an output signalindicating presence of a fluid and/or causing activation of externaldevices. Such electrical potential, hereinafter referred to as a "fieldeffect", is caused by the differential charge between the probe and thepositively charged molecules comprising the detected fluid into whichthe probe has been partially immersed. This field effect provides thework necessary to liberate electrons within the probe or within materialencasing it, and the liberated electrons comprise current flow which isrouted to the oscillator circuit, thereby causing oscillation upon theoccurrence of certain conditions, resulting in transmission of an outputsignal to initiate performance of a given task.

Structure of the Preferred Embodiment

FIG. 1 shows a block diagram of an apparatus for detecting a givenfluid, such as water, and which can cause activation of external device,such as an alarm or sump pump upon detection. The device chieflycomprises one or more probes, such as at 1, 1', and 1". A sensor pad 31detects a given fluid in response to the field effect between the sensorpad 31 and fluid into which a probe 1 containing sensor pad 31 isimmersed (see FIG. 3). The term "immersed" is used herein to refer toeither partial or total immersion of the pad 31 into the fluid. Theprobe 1 may be immersed into a naturally occurring body of fluid, or itmay be immersed into a fluid 70 contained by an enclosure. 72, such as atank.

When the field effect is generated and when fluid is present whichcorresponds to a resistor 16 in an oscillator circuit 2 (FIG. 4), aswill be described in greater detail herein, current within theoscillator circuit 2 begins to oscillate. These oscillations take theform of AC signals which are detected by a detector circuit 3interfacing with the oscillator circuit 2. The detector circuit 3modifies the AC signal and then sends it to an interfacing amplifiercircuit 10 (FIG. 4), from which it proceeds to an output circuit 4,which converts the modified, amplified AC signal into a logic signal.That logic signal is sent via leads, such as at 11, to a control unit 5.The control unit 5 then, depending upon the state of the logic signal,can indicate the presence of a liquid, the liquid level in an enclosureonce the depth of insertion of the pad 31 into the enclosure is known,turn on an alarm 7, or activate another external device, such as a sumppump 6, which would start removing the detected liquid. In the latterarrangement, control unit 5 could also actuate monitoring means, such asa 2-digit LCD counter, each time sump pump 6 is activated, therebyenabling a user to monitor the number of cycles performed by sump pump6. In the absence of control unit 5, the function of the logic signalfrom output circuit 4 is limited to activation of an LED light 41.

Having described the invention in general terms, the invention will bedescribed in more detail with attention being directed to FIGS. 2-4.

FIG. 2 shows a probe 1 used in the present invention. The probe 1comprises a printed circuit (PC) board 30 encapsulated by a pottingmaterial 33a, 33b, which is preferably an epoxy resin. Surrounding thepotting material 33a, 33b is an inert and non-conductive shell 40. ThePC board 30 has a pad area 31, which is constructed of a metallicconductive material, and a circuit area 32. The circuit mounted to thecircuit area 32 is shown in FIG. 4 and will be described in detailbelow. Finally, extending from the PC board 30 are an output line 34, a+12 Volt DC power supply line 36, and a ground line 35.

In the pad area 31 of the PC board 30, an additive 42 comprised of atomscharacterized by a low ionization potential, such as graphite orpowdered silver, is added to the potting material 33a. The enhancedpotting material increases the effective area of the pad 31 byincreasing the sensitivity of the probe to positively charged molecules.While additive-to-potting ratios on the order of 0.5-1.0 grams/ounce areacceptable, sensitivity of the probe is reduced by 60% when going from1.0 grams/ounce to 0.5 grams/ounce.

The sensitivity of the pad is determined not only by the amount ofadditive in the potting mixture but also by the dimensions of the paditself. The Sensitivity factor (S_(f)) of the probe is determined by thefollowing formula:

    S.sub.f =(100/A)*(b/c)

Wherein:

S_(f) =sensitivity factor

A=Pad area (sq. cm)

b=quantity of resin (mg)

c=reciprocal of concentration of resin to additive ratio (e.g.,4:1=0.250)

The sensitivity of the pad determines the depth of its immersion, intothe fluid being analyzed, at which it can detect a particular fluid. Forexample, a probe with a high sensitivity would only need to be insertedabout 3/8" into the fluid, while a probe with a low sensitivity wouldhave to be inserted much deeper, for example 3/4".

Once the pad area 31 has been coated with the epoxy resin material 33a,33b, the fluid need not be in direct contact with the sensor pad 31.Therefore, the sensor pad 31 can be enclosed in a protective shield 40made of inert and non-conductive material such as PVC, which is anexcellent material for this application because not only is itchemically inert but it is also a non-conductive material through whichthe field effect is still felt, due to the enhanced sensitivity of thepad stemming from the additive-laden potting material 33a, 33b. This PVCshell 40 strictly protects the probe from contaminates that may be foundin the fluids.

The principal behind the operation of the probe 1 is the fact thatunctuous fluids, i.e., those containing fats or oils, containhydrocarbon molecules, which are known to generally have a positivecharge. If the charge within the fluid is more positive than the chargedprobe 1, the sensor pad 31 will detect that difference and generate anoutput. Similarly, if the fluid is more negatively (e.g., lesspositively) charged than the sensor, an output is likewise generated.

FIG. 4 shows the circuit 50 controlling the detecting device constructedin accordance with the preferred embodiment. When the field effectoccurs between the probe 1 and the fluid into which it is immersed, itcauses the easily-liberated electrons in the potting material additive42 (FIG. 2) to flow as current through output 34 and into oscillatorcircuit 2. If the resistance in a resistor 16 of that circuitcorresponds to a particular fluid present in the fluid being detected byprobe 1 (hereinafter referred to as "oscillation conditions"), as willbe explained in greater detail herein, the current flowing throughoscillator circuit 2 will begin to oscillate.

The oscillator circuit 2 is primarily comprised of a first capacitor 14and an inductor 15 connected in series to the pad 31, and of a resistor16 connected in parallel to the inductor 15. The component values of theoscillator circuit 2, i.e., the resistance of resistor 16, thecapacitance of capacitor 14, and the inductance and "Q-value" (anindicator of the capacity of an inductor to generate an electrical fieldthereabout) of inductor 15, preferably allow the oscillator circuit 2 tosustain a frequency of approximately 10 MegaHertz, although oscillationat different frequencies is contemplated by the present invention.

The current flowing into oscillator circuit 2 causes a change in voltageacross a second capacitor 12, which is felt by the transistor 13.Transistor 13 is biased to be activated responsive to a slight change inthe voltage across second capacitor 12. If oscillation conditions arepresent, transistor 13 will send a signal to the remainder of circuit 50responsive to oscillating current. That current oscillates by firstflowing through inductor 15, then onto a plate of capacitor 14, therebybuilding charge thereon. As that charge builds, the electric fieldaround inductor 15 collapses, which, in turn, causes the capacitor 14 todischarge. The charging and discharging of capacitor 14 is cyclic;consequently, the corresponding voltage change across capacitor 12 islikewise cyclic. Responsive to this cyclic change of voltage, transistor13 periodically transmits current, now in the form of an AC signal, tothe remainder of circuit 50.

The AC signal from transistor 13 is felt across a resistor 17interfacing with a detector circuit 3, into which the AC signal enters.The detector circuit 3, by use of capacitor 18 and diode 19, removes thenegative portion of the AC signal. The remaining positive portion of theAC signal causes an amplifier circuit 10 to drive an output circuit 4 toproduce a logic high output. Capacitor 18 also prevents any DC potentialfrom transistor 13 from reaching a transistor 20 of amplifier circuit10.

The output circuit 4 sends a signal sufficient to cause transistor 20 toturn on and gate the signal to output transistor 21. When transistor 21is turned on, a voltage drop across resistor 22 is felt and represents alogic high signal to be sent to control unit 5 (FIG. 1) which can beused by any associated circuitry. For example, control unit 5 may be anoutput microprocessor, such that the resulting output signal from outputcircuit 4 may be transmitted to the out microprocessor, which cancontain logic to perform the turn on-off functions of the sump pump,sound an alarm, etc.

When the sensor pad area 31 is removed from the fluid, the charge acrosscapacitor 12 equalizes, and transistor 13 becomes inactive. Therefore,oscillations cease.

The resistance R1 of resistor 16 determines how much of a difference inpotential between pad 31 and the fluid is required before theoscillations in the oscillator circuit 2 begin. Therefore, the value ofR1 determines what fluid will be detected by the pad. Table I showsvarious values of R1 and the fluids to which they correspond.

                  TABLE I                                                         ______________________________________                                        R1 (kOhms)          Material                                                  ______________________________________                                        1.0                 Nothing                                                   2.8                 Aviation Fuel                                              3.08               Water                                                     4.3                 Kerosene                                                  5.2                 Cooking oil                                               6.2                 40 Weight Oil                                             10.0                Air                                                       ______________________________________                                    

At a particular value of R1, only detection of that particular materialwill be accomplished; the presence of any other material is ignored.Furthermore, it has been determined through experimentation that slightchanges in the value of R1 can enable detection of different fluids. Ascan be seen from this chart, as the value of R1 increases, the probe candetect heavier and heavier hydrocarbon molecules while ignoringeverything else.

Referring again to FIG. 4, if the detection device of the presentinvention is intended for broad application, meaning that it iscontemplated that the device would detect a number of different fluids,a potentiometer 100 (variable resistor) may substitute for resistor 16,and it may be communicate with oscillator circuit 2 via leads 102connected to resistor terminals 103. Thus, various values of R1 can beused in the detection device, using a single probe, to adjust fordetection of different types of fluids.

Alternatively, because the value of R1 determines what fluid isdetected, the detector of the present invention can be constructed toidentify an unknown fluid. Instead of using either resistor 16 orpotentiometer 100, another microprocessor 105 can interface with circuit50, such as by being connected to terminals 103 via leads 106. Once theprobe is immersed into a fluid, microprocessor 105 is activated toautomatically and continuously substitute a plurality of differentvalues for R1 until oscillation conditions occur at a particular valueof R1, at which time microprocessor 105 actuates an indicatoridentifying a fluid into which the probe is immersed. Such an indicatormay be a series of lights, each light configured to be lit responsive toa corresponding R1 reading at the time of oscillation conditions. Apanel housing the lights could bear indicia setting forth the name ofthe fluid corresponding to each R1 value. This embodiment of the presentinvention may therefore quickly identify an unknown fluid.

It is important to note, however, that the varying of R1 is not the onlyway to detect different fluids or to achieve broad application or fluididentification. For instance, the "Q-value" of inductor 15 can bechanged to achieve the same results.

Structure of a Modified Embodiment

A modified embodiment of the present invention differs from thepreferred embodiment in two respects: (1) the pad area of the probe isbare, being neither encased in a potting material nor enclosed within aPVC shell, and (2) an additional capacitor is interposed intermediatethe probe and the oscillator circuit.

First, as previously stated with regard to FIG. 2, pad area 31 isconstructed of a metallic conductive material. A preferable material fora bare pad area is 316L stainless steel. Thus, the pad 31 of thisembodiment directly contacts the fluid into which it is immersed.

Second, referring to FIG. 5, a third capacitor 60 is interposed in theoutput 34 connecting the pad 31 and the oscillator circuit 2. Theremainder of the circuit is identical to circuit 50, described withregard to the preferred embodiment. Third capacitor 60 removes DCpotential that would otherwise be applied to pad 31, thereby preventingelectrolysis of the fluid into which pad 31 is immersed. Despite thefact that the pad 31 in this embodiment is not charged, a field effectis still generated between it and the fluid due to the molecularstructure of the stainless steel or other metal comprising the pad 31.If oscillation conditions are present, this field effect causesoscillation in the same manner as described with regard to the preferredembodiment.

Operation of the Embodiments

The structures of the respective embodiments of the invention havingbeen described, operation of a detector constructed in accordance witheither embodiment will now be described.

A particular use foreseen for the detecting device according to theinvention is determining whether water has been mixed with oil. For thisparticular use, the value of R1 would be set to 3.08 kOhms and the probe1 placed to the appropriate depth in the fluid source in accordance withthe S_(f) of the pad area. When no water is present, the pad 31 detectsnothing and no oscillation occurs. This is because at this value of R1,the probe ignores everything but water. However, as soon as water isdetected, the potential between it and the pad 31 will cause oscillationof current within the oscillator circuit 2. Then, the signal will besent through the rest of the circuit and to the output circuit 4 of thedetector. This output signal can activate an LED light, such as at 41(FIG. 1) to detect the presence of water. If a microprocessor 5 isconnected to the output circuit 4, the output signal can additionallycause the activation of an alarm 7. Such an arrangement may be employedto detect water in aviation fuel tanks or other tanks where the presenceof water is not desirable.

The arrangement described immediately above could also be used inconnection with concrete preparation, i.e., the detecting device canindicate when a concrete mixture has been cured. A probe, which would beused one time only, is inserted into a fresh concrete mixture. The fieldeffect between the probe and the water in the mixture would be feltthrough the other concrete ingredients. In a sample constructionaccording to this arrangement, an LED light may be activated until theportland cement in the concrete has been completely hydrated, at whichtime there would be no free water particles in the concrete left tocause the field effect.

As shown in FIG. 1, the detection device of the present invention canemploy more than one sensor arrangement. Where two sensor arrangementsare used, two types of fluids, such as oil v. water, can bedistinguished, resulting in activation and deactivation of externaldevices. In such an instance, two sensors are employed, the sensorarrangements being identified as Types A and B, each sensor arrangementhaving oscillator circuit resistors of different resistances. Here, thefirst sensor (Type A) is set to detect oil only, while the second sensor(Type B) is set to detect water only. Both sensors are placed in thefluid, and as each detect their respective fluids, a microprocessor 5can be used to determine the relative amounts of each.

The above dual sensor arrangement would be useful for determining thepercentage of water emulsion in oils and for detecting oil spills at seawhen placed on buoys. The greater the degree of refinement of oil, theeasier it is for the Type A sensor to detect. Specifically, preparatoryto an oil refinement process, positively charged plates are immersedinto the crude oil to attract the negatively charged particles, i.e,water particles, thereto, thereby extracting them from the oil.Therefore, the greater the amount of refinement, the easier it is todetect the oil, e.g., aviation fuel is more refined than 40 weight oil.

The above dual sensor arrangement may also cause activation anddeactivation of a sump pump, a function having particular applicationfor natural oil storage tanks. Since extracted natural oil frequentlycontains ground water, the storage tank often contains a stratum of oilseparated from and superposed upon a stratum of water. The detectiondevice of the present invention can be lowered/installed into the oilstorage tank both to determine the presence of water levels and to causeactivation of a pump to remove the water only. When the Type B sensordetects water, its associated circuit is activated to cause activationof the sump pump to evacuate the water from the tank. When suchevacuation is complete, the Type A sensor would detect the oil and senda signal to deactivate the sump pump. This would prevent the loss of oilbeing pumped with the water. A device constructed according to thisarrangement could also be used in ship bilges and in processing tanksfor cooking oils.

A multiple sensor arrangement could be used for detecting ground watercontaminants. Such an arrangement contemplates a Type B sensor and amultiplicity of Type A sensors, each Type A sensor being set to detectdifferent types of contaminants.

The above description is given in reference to a detection device.However, it is understood that many variations are apparent to one ofordinary skill in the art from a reading of the above specification andsuch variations are within the spirit and scope of the instant inventionas defined by the following appended claims.

That which is claimed:
 1. A method for determining presence of water ina fluid, comprising the steps of:providing a probe responsive only tothe presence of water; placing the probe in a supply of fluid; anddetermining the presence of water in the fluid responsive to an outputsignal of the probe representative of an electrical potential betweenthe probe and the fluid having a predetermined value.
 2. The methodaccording to claim 1 wherein:the probe includes an oscillator circuit;and the step of providing a probe responsive only to the presence ofwater includes providing a resistor in the oscillator circuit, theresistor having a resistance which permits oscillation in the oscillatorcircuit responsive only to the predetermined electrical potential.
 3. Amethod for determining presence of water, comprising the stepsof:providing a probe which includes an oscillating circuit responsiveonly to the presence of water; and determining the presence of waterresponsive to an output signal of the probe representative of anelectrical potential having a predetermined value which permits theoscillating circuit to oscillate.
 4. A method according to claim 3,wherein the step of providing a probe responsive only to the presence ofwater includes providing a resistor in the oscillator circuit, theresistor having a preselected resistance which permits oscillation inthe oscillator circuit responsive only to the predetermined electricalpotential.